Fias Stijn, Van Damme Sofie, Bultinck Patrick
Department of Inorganic and Physical Chemistry, Ghent University, Krijgslaan 281 (S3), 9000 Gent, Belgium.
J Comput Chem. 2008 Feb;29(3):358-66. doi: 10.1002/jcc.20794.
The aromaticity and local-aromaticity of a large set of polycyclic aromatic hydrocarbons (PAHs) is studied using multicenter delocalization indices from generalized population analysis and the popular nucleus independent chemical shift (NICS) index. A method for the fast computation of the NICS values is introduced, using the so-called pseudo-pi-method. A detailed examination is made of the multidimensional nature of aromaticity. The lack of a good correlation between the NICS and the multicenter delocalization indices is reported and the grounds discussed. It is shown through a thorough statistical analysis that the NICS values arise not only from local aromaticity of the benzenoid rings, but also from other circuits. It is shown that the NICS indices do not reveal the individual aromatic nature of a specific ring, contrary to the delocalization indices.
利用广义布居分析中的多中心离域指数和广为人知的核独立化学位移（NICS）指数，研究了一大组多环芳烃（PAHs）的芳香性和局部芳香性。引入了一种使用所谓的伪π方法快速计算NICS值的方法。对芳香性的多维性质进行了详细研究。报道了NICS与多中心离域指数之间缺乏良好的相关性，并讨论了其原因。通过全面的统计分析表明，NICS值不仅源于苯环的局部芳香性，还源于其他环电流。结果表明，与离域指数相反，NICS指数不能揭示特定环的个体芳香性质。
